Process of purifying sodium-phosphate waste liquors.



-iion, of the silk would result.

UNITED sTATEs PATENT curios. .i

HERMANN Lair, or EL EBFELD, GERMANY.

raocnss or PURIFYING somum-rnosrnnrnwasrn mavens.

No Drawing.

To (db whom it may concern: Be it known that I, HERMANN Ln'Y, a subect of the King of Prussia, German Em- 4 peror, and a resident of Elberfeld, German Empire, have invented certain new and'usefful Improvements in Processes of Purifying Sodium-Phosphate Waste Liquors, of which the following is an exact specification.

Qof sodium phosphate employed in silkweighting will take up compounds, of tin which accumulate in these baths. When the upercentage of tin contained in a bath exceeded a certain limlt 1t was necessary to abandon the bath and substitute a new one,

I as there exis ed no useful process for separating these injurious compounds of tin from a bath of sodium phosphate and restoring the bath to a condition in which it was -fit for use again for the purpose of weighting silk. The separation of the compounds of tin from such a bath is attended with considerable difiicult-ies, as the precipitating agents generally used for precipitating compoundsof tin either cause no separation at all or else an utterly incomplete separation of the compounds of tin-and this is true both in the case of chemical action, as by means of caustic alkali, sulfureted hydrogen, etc., and

in the case of electrolytic action.

Now I have found that tin separates quickly and quantitatively fromsuch'a bath if first there be added to the bath small quantities of the salts, soluble in water, of such mctalsas have phosphates. nsoluble in wa tea -and the bath then be suitably heated. The soluble salts of calcium, barium, strontium, magnesium, zinc and aluminum may be used for this purpose. Of the soluble salts tested by me up to the present time I have found that the following give a greater or less precipitation of'the tin, according to the quantities added: Calcium -oxid, chlorid, n trate and acetate. Barium-oxid, chlorid and nitrate Sti'ontium-oxid, chlorid and nitrate. -Magnesiumoxid, chlorid, nitrate, sulfate, acetate, and mixture of magnesia.

Specification of Letters Patent.

Application filed April 27, 1910. Serial No. 557,951.

I Zinc--chilorid,

Patented Jan. '7, 19 13.

nitrate, sulfate, acetate. Alum1numchl0r d, sulfate, acetate, acetotartrate. By adding the proper amountof any such salt to what would ordinarily be the waste liquor of the bath a precipitate will be formed containing all of the tin present in the bath. By filtration aperfect separation of the preci itated compounds of tin may be veifected an the bath restored to a condition inuivhich it'is fit for use again for weighting si t In order that my process may be clearly understood}. give the following example illustrating one mode of practising it: 4 kilos.

of magnesium sulfate dissolved in a small quantity of water are added to 1,000 liters of a bath of sodium phosphate containing. 2 golf tin in each liter of solution: These baths, as used in silk-weighting, on an average contain from 160 to 200. g. of sodium phosphate (Na,HPO,, 121-1 in one liter. The highest possible concentration, accord ing'to my experience, would be from 250 g. to 270 g. of sodium phosphate in one liter.

After the magnesium sulfate has been added 80 to the bath the whole is carefully stirred- ,The bath, which has become slightly turbid,

is then heated up to the boiling point and after a few minutes is left to cool, after which it is forced through a filter-press. The solution obtained is entirely free from tin and may be used again for silk-weighting purposes. The precipitate contains about per cent. of tin, which may be recovered by treating the precipitate in any of the well-known ways. v

The great importance of this process in the silk-weighting industry will be readily understood when it is considered that it has been'necessai-y heretofore not only to abans don the baths themselves after they had accumulated a certain percentage of tin, but also to lose a large part of the sodium phosphate taken up by the silk in passing through the baths. After treatment this 100 "to centrifugal action after having passed 0 l through four baths, and been normally weighted, about per cent. of the sodium phosphate taken up in the baths by. the silk will be removed. This considerable amount of sodium phosphate, which has been a total 1 phosphates of which are ing such a liquor with a salt, soluble in Water, of a metal the phosphate of which is insoluble in Water, and heating the liquor.

4t. A process of purifying sodium phosphute Waste liquors, which consists in treating such a liquor with soluble salt of a metal the phosphate of which is insoluble in Water, and heating the liquor up to the boiling point. 1

5. A process of purifying sodium phospurifying sodium phospurifying sodium phos phate Waste liquors, which consists in treat my hand in the presence oi two witnesses osepeo phste Waste liquors, Wl ich consists iu tresting such it liquor with magnesium sulfate.

A process of purifi ing phate Waste liquors, which consists in treat ing such av liquor with a small quantity of e solution of magnesium sulfate, and then heating the liquor.

A process of purifying sodium phospligite Waste liquors, which consists in treat h s. such z-i liquor with a small quantity of :2

solution of magnesium sulfate, and then. heating the liquor upeto the boiling point.

8. A process of purifiing sodium phosphate waste liquors, which consists in treat ing such a liquor Water, of a metal the phosphate of which is insoluble in Water, hosting the liquor to the boiling point, and after cooling separating the precipitate.

In Witness whereof I have heruu to set 4 HERE- ANN llituesses OTTO Komo, VVALTER Vommoc'r.

sodium phos with a salt, soluble in 

